Radio receiving apparatus



y 1932 s. TARZIAN I 7 RADIO RECEIVING APPARATUS Filed July '7, 1950 [flue/1 Zor m v5 {milk '81 other than Patented July 12 1932 UNITED STATES PATENT:- OFFICE SARiKES TARZIAN, F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO A'IWATER KENT MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA RADIO RECEIVING APPARATUS Application filed. July 7, 1930. Serial No. 465,831.

My invention relates to radio receiving apparatus, and particularly to receiving systems or sets in which occur or are produced oscillations, more particularly of radio frequency, those representing the received signals.

Where the electric power for a receiving system is derived from alternating or direct current lighting or power circuits, oscillalotions, other than those representing the received signals, occurring or purposely generated in the system, will in many cases pass by conduction or otherwise over or along the conductors of the lighting or power circuit into other apartments or home in which are receiving systems similarly receiving power from the same lighting or power circuit or whose input systems are Within the radio frequency influence of the conductors of the lighting or power s stem, causing whistles,

squeals or like distur ances.

It is the object of my invention to prevent a receiving system or set from so influencing others, and to this end I provide means, such 95 as a filter system or equivalent, interposed of any suitable type, such as comprises induc between the power or lighting system and the set in which oscillations occur or are generated, to eliminate or to reduce to insubstantial magnitude any such oscillations from or in 9 the lighting or power system.

In accordance with myiinvention, a filter tive and capacitative reactances suitably related, is interposed between the power or lighting s stem and the receiving system or set in which os'cillationsoccur, or are purposely produced as in heterodync and superheterodyne systems. I

My invention resides in a system and apparatus of the character hereinafter described and claimed.

For an understanding of my invention reference is to be had to the accompanyin drawing, which is a diagrammatic view 0 a portion of a superheterodyne receiver embodying 'quence varied as to their frequency a direct or alternating current power or lightin system.

eferring to the drawing, V is the first detector tube, havin the cathode 0, control grid 9, screen or shiel grid 8, and plate or anode a. The cathode c is maintained at suitably high temperature by the electric heater h.

Associated with the antenna A, or any equivalent absorption structure, is the primary 'p of an input transformer, preferably adjusted as to its number of turns by the switch 0?, and having one terminal connected to earth E, or equivalent counter capacity or ground, as the metal chassis of the receivin set. Between the primary p and the inpu electrodes of the detector V are cascaded circuits tunable respectively by the variable condensers C and C1, for tuning to the desired'signal, which in broadcast reception represents generally speech or music.

There is impressed upon the input system of the detector V, b the transformer t oscillations locally p'ro need or generated cillations is determined by variation of the capacity of the condenser 02, whose movable or adjustable element is preferably mechanically connected to the movable or adjustable elements of the-tuning condensers C and C1, as. indicated by the broken line 1. The oscillations generated by the tube 0 are in consebut differ from the signal fre uency to a predetermined extent producing a cat current or current of intermediate frequency.

By a coupling between the plate circuit of the tube V and the input of the first intermediate frequency amplifier Vl, there is imressed upon the latter a beat or intermediate requency voltage. The plate circuit of the tube V1 is coupled to the input of the second intermediate frequency amplifier tube V2 through any suitable coupling, which, in the example illustrated, comprises an inductance L shunted by capacity ()3 tuned to a narrow band of frequencies within which lies the the tubes descr1bed,= and for the audio freguency amplifier tubes, not shown, is derived rom a supply system whose conductors are indicated at 2 and 3, generically representing either a direct or an alternating power or lighting system, ordinarily a commerclal system, from which the power for other receiving systems or sets is derived.

n the example illustrated, the circuit 2, 3 delivers alternating current to the primary P of the transformer T, having a secondary S with which is associated the usual double wave rectifier tube V4, whose cathode f isheated by current from the secondary S1. At the terminals 4 and 4a appears a rectified filtered or uni-directional voltage suitable for the plate circuits of the various tubes.

When the cathodes of the tubes are filaments themselves heated by current, or when, as illustrated, electric heaters h are employed, the receive current from the secondary S2, or rom several such secondaries. The heater k for the oscillator O is shown connected across the secondary S2, and this is exemplary in general of the other heaters h, which are i usually similarly connected.

ing systems,

"recelving power Even though the oscillator O. and its circuits are shielded, which it may be as indicated by D, to prevent influence upon different parts of the receiving system of which it is a part, or to radiate to neighboring receivother receiving sets or systems from the same circuit 2, 3 will or may have transmitted thereto, over the power wires, oscillations from the set comprising the oscillator O; and these oscillations become in the other sets disturbing oscillations, producing audio frequency disturbances, such as squeals or whistles, or otherwise interfere with complete independence of operation or control of such other receiving sets.

From the oscillator O oscillations will reach the power system 2, 3 through various paths within the receiving" set. In the example illustrated, oscillations will appear in one or more of the transformer secondaries,

.will pass over them to other sets connected to branches such as 5, 6 or 7, 8, as in different residences or apartments receiving lighting or power current from the same system 2, 3.

The receiving set is connected to the power system 2, 3 generally through an attachment plug, lamp socket or the like, whose coacting .contacts are indicated at 9 and 10. Between this switch 9 and 10 and the receiving set, and specifically between that switch and the primary P of the transformer T, is inserted, in accordance with my invention, means for eliminating from the power mains 2, 3 and efiect of the oscillations produced within the receiving set, and particularly there is eliminated from the power mains any effect of the oscillations produced by the generator 0. The elimination is either complete or of such high magnitude that the oscillations, if they reach the circuit 2, 3, are of insubstantial magnitude.

For my purposes, be employed which has generally the efiect of a filter system, which is the means in the example illustrated. This filter s stem comprises the series inductances L1, 2, disposed between the condensers K1 and K2.

Such a filter system, or equivalent means, is utilized preferably in addition to the condensers K3 and K4: in series across the primary P, with a connection from a point between them to earth or ground E;

The filter system may be provided as a separate unit, or, and preferably, is comprised within the receiving set whose input power terminals are in a relative position, electrically2 speaking, indicated by the points 11 and 1 Each of the inductances L1 and L2 may be of 300 microhenries, and each of the condensers K1 and'K2 may then have a capacity of .01 microfarads. Through the inductances is passedthe power current for the set; the conductor of which the inductances are wound is suitably large for that current. A filter system of these proportions will suffice to prevent access to the power system 2, 3 of oscillations ranging in frequency from 680 'kilocycles to 1630 kilocycles,which may be the fre uency range of the oscillator or generator for pill'oducing an intermediate frequency of 130 'locycles, for the present broadcast frequency range.

Similarly, the filter, such as L1, L2, K1, K2, prevents entry into the set or system of oscillations within the frequency range of the filter existing in the power system 2, 3, and which might be impressed thereon from some other receiving set in which oscillations occur or are generated;

What I claim is:

1. The combination with a power circuit, of a heterodyne receiving system comprising vacuum tubes receiving their powerv from said circuit, means for tuning said receiver through a range of signal frequencies, means within said receiver and including one of said any suitable means may tubes for locally producing oscillations of frequencies within said range of signal frequencies, and means for preventing impression of said locally produced oscillations through said power circuit u on other receiving systems supplied there y comprising a capacitative and inductive filter interpose between said power circuit and the powerinput terminals of said heterodyne receiving system and .whose constants are suited substantially to preclude transfer to the power circuit of the oscillations locally produced by said means.

2. The combinationwith a power circuit, of-a heterodyne receiving system comprising vacuum tubes receiving their power from said circuit, means for tuning said receiver through a range of signal fre uencies, means within said receiver and inclu 'ng one of said tubes for locally producing oscillations of frequencies within. said range of signal frequencies, and means for preventing disturbance of other receivers supplied with power from said circuit comprising shielding structhe power circuit of the locally produced 0sture for said local oscillation producing means and a capacitative and inductive filter interposed between said power circuit and the power input terminals of said heterodyne receiving s stem and whose constants are suited su stantially to preclude transfer to cillations.

SARKES TARZIAN. 

